1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof.
2. Description of the Related Art
A conventional semiconductor device for current detection use including a Hall element is disclosed in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2001-230467.
FIG. 1 is a diagram showing the structure of a conventional semiconductor device 101. As shown in FIG. 1, the semiconductor device 101 comprises a semiconductor base 103 in which a Hall element 102 is formed, and a plate-like wiring layer 104 which is so provided as to surround the Hall element 102 as viewed from the top.
The wiring layer 104 is connected to an unillustrated measurement target circuit to constitute a path for a measurement target current. By a current flowing through the wiring layer 104, a magnetic field is formed around the wiring layer 104. The Hall element 102 detects the magnetic field formed around the wiring layer 104 by utilizing the Hall effect.
The wiring layer 104 is constituted by a U shape portion 105 which partly surrounds the Hall element 102, and pad portions 107 to which wires 106 to be connected to the measurement target circuit are connected as viewed from the top. A current from the measurement target circuit is supplied via the wires 106 to the pad portion 107 on one side, flows through the U shape portion 105 to reach the pad portion 107 on the other side, and returns via the wires 106 to the measurement target circuit
Due to the current flowing through the U shape portion 105, a stable and relatively strong magnetic field is applied to the Hall element 102 arranged inside the U shape portion 105. The Hall element 102 is used to detect a magnetic field applied thereto, to detect whether there flows any current, or to measure the level of a current, by utilizing the Hall effect.
The wiring layer 104 is formed on the semiconductor base 103 via an insulation film. Generally, an insulation film having a sufficient thickness is necessary in order to ensure a sufficient withstand voltage. In many cases, an insulation film is made of a silicon material such as silicon dioxide, etc. However, it is difficult to make an insulation film made of a silicon material thick. To deal with this problem, there has been developed a method of stacking upon the silicon film, an organic film which is easy to make thick, such as a resin film made of polyimide resin.
FIG. 2 shows a sectional view of the semiconductor device 101 comprising such an organic film. FIG. 2 shows a sectional view of the semiconductor device 101 as sectioned along a line B—B shown in FIG. 1. As shown in FIG. 2, a thick organic film 108 is formed on a thin silicon oxide film 109 formed on the semiconductor base 103. The wiring layer 104 is formed on the organic layer 108 and is therefore electrically insulated from the semiconductor base 103 by the organic film 108 and the silicon oxide film 109. By forming the thick organic film 108, a sufficiently high withstand voltage can be ensured. Also by forming the thick organic film 108, it is possible to flatten the surface on which the wiring layer 104 is formed and to realize a strong bonding strength.
In the above-described semiconductor device 101, the wiring layer 104 is directly formed on the organic film 108. The wiring layer 104 is made of metal such as copper, etc. Generally, metal and an organic material can not adhere to each other strongly, which means that the organic film 108 and the wiring layer 104 are easily separated from each other. Therefore, the wiring layer 104 might be separated from the organic film 108 in a wire bonding process or in a heating process. Accordingly, there is a problem that the above-described structure can not achieve a semiconductor device having a high reliability.
The content of the above-mentioned Unexamined Japanese Patent Application KOKAI Publication No. 2001-230467 is incorporated herein by reference.